The need for high-density recording has increased in recent years, and thus magnetic recording media having good electromagnetic characteristics have been demanded. Reliability is also required in the repeated accessing and storage of data. Accordingly, magnetic recording media are required to have both good electromagnetic characteristics and good running durability.
Conventionally, magnetic recording media having a magnetic layer comprising iron oxide, Co-modified iron oxide, CrO2, ferromagnetic metal powder, and/or hexagonal ferrite powder dispersed in binder and disposed on a nonmagnetic support have been widely employed. Of these, microparticulate ferromagnetic alloy powders and hexagonal ferrite micropowders are known to afford high-density recording characteristics. However, when employing inductive heads that have been mainly employed in systems employing flexible media, these ferromagnetic powders have afforded low levels of saturation magnetization, precluding adequate output. However, the use of the magnetoresistive heads (MR heads) employed with hard disks has begun even in removable recording employing the above-mentioned flexible media.
The size of the MR elements in MR heads has decreased as higher density levels have been achieved. However, the smaller MR elements emit heat when even a small current is passed through them, causing the temperature to rise sharply. When a head at high temperature comes in contact with the surface of the magnetic layer of a tape on which impurities are present, a burning phenomenon occurs and material adheres to the head. Such head deposits cause an increase in the error rate with repeated running.
Accordingly, the quantity of abrasive added to the tape has been increased and large particle abrasives have been employed to reduce head deposits. However, although such methods bring about improvement in the error rate caused by head deposits, they have a drawback in the form of considerable shortening of the service life of the head. In particular, the computer data storage tapes of recent years have tended to become thinner and the wavelength of the recording signal to become shorter in order to increase storage capacity. In such magnetic tapes, even spacings due to deposits of several tens of nanometers decrease the reproduction output to deteriorate the error rate. Further, the reduction in head size is continuing and even slight head abrasion quickly increases the error rate.
In order to reduce head deposits, it was proposed to specify the quantity of fatty acids extracted from the magnetic layer and the quantity of water-soluble metal ions to reduce the level of precipitates following storage at high temperature and high humidity (Japanese Unexamined Patent Publication (KOKAI) Heisei Nos. 7-296360 and 7-296366). According to the techniques described in the above publications, the level of precipitates due to storage could be reduced, but due to the low level of fatty acids, there is a problem in that more matter adheres to the head with repeated running and the error rate increases.
It is an object of the present invention to provide a magnetic recording medium having excellent electromagnetic characteristics with reduced head deposits.